The inventions relates to a pump with one or more pistons which can be rotated, as well as to a method for compensating for abrasion-wear of a pump piston.
For rotating piston pumps, especially for conveying liquids laden with solids, there must be a seal between the rotating piston or pistons and the wall of the pump space and, in the case of several pistons, also between the individual pistons. The efficiency achieved varies with the quality of the seal with the wall and the quality of the seal between the pistons.
The DE 20 02 518 C3 shows an elastomeric coating for rotating pistons of pumps, which are used to convey solid-laden suspensions. Such a coating can yield elastically, if solid particles penetrate into the gap between the piston and the wall or into the gap between the rotating pistons, which are as close to one another, as possible. By these means, blockage of the rotational movement by solids is prevented.
However, the outer elastic layer or the piston is subject to increased wear, particularly by such particles penetrating into the respective gap. As the wear increases, the thickness of the plastic layer becomes less and, with that, the gap between the piston or pistons and the wall becomes greater, as a result of which the efficiency of the pump decreases. However, an exchange of pistons, which then becomes necessary, is very expensive.
The EP 0 599 333 B1 therefore shows piston parts, which can be exchanged individually, without having to exchange the whole piston. For this purpose, the blade tips are constructed as sealing strips, which can be slipped on and are fastened in a dovetail guide and can be exchanged when necessary. However, the manufacturing costs of such a design are very high. Moreover, in the case of multi-bladed pistons, all piston tips generally must be exchanged simultaneously, so that the maintenance costs, as a whole, are increased for such an exchange, since the number of parts, which must be exchanged, has grown appreciably in comparison to exchanging a piston. Moreover, the practical construction of such a dovetail guide is very expensive.
It is an object of the invention to counteract the wear-induced abrasion of an outer polymer layer of a pump piston with the least possible expense.
An adjustment of the outer, wear layer of the piston is made possible by the inventive construction of a pump. Due to the introduction, as required, of a supporting body in the designated recess, a thinning of the material of the polymer layer can be taken into account, in that the recess is expanded by introducing the supporting body. By these means, the polymer layer is stretched approximately to its original thickness. Such a recess can extend essentially along a line of contact between the piston and the wall of the pump space and thus counteract a radial thinning of the outer polymer layer by introducing a supporting body. The recess can also be disposed essentially perpendicularly to the axis of rotation, so that the introduction of the supporting body expands the piston regions, which form a seal, transversely to the axial course against the wall of the pump space and are also exposed to wear.
If an assortment of different supporting bodies of different dimensions is available, a wear-related material thinning of different extent can be taken into account particularly advantageously.